1. Field of the Invention
This invention relates to an IEEE 802.16 system or other wireless communication system obtaining a base station device and a relay station device which relays information, and which also obtains a wireless terminal device which performs wireless communication with the base station device via the relay station device, in which wireless frames are repeated with a fixed period. This invention also relates to the relay station device and base station device used in the wireless communication system.
Priority is claimed on Japanese Patent Application No. 2004-253950, filed Sep. 1, 2004, the content of which is incorporated herein by reference.
2. Description of the Related Art
In the IEEE 802.16 standard for high-speed wireless data communication (hereafter called “the 802.16 standard”), P-MP (point to multipoint) and mesh network architectures are defined for communication. In a P-MP architecture, a BS (base station) schedules opportunities for transmission and reception of all SS (subscriber stations), therefore, communication which is efficient and ensures QoS (Quality of Service) is possible. On the other hand, in a mesh architecture multi-hop communication between terminals is possible, and transmission opportunities are adjusted by surrounding terminal groups. Thus scheduling differs according to the network architecture, therefore, the wireless frame structure also differs greatly for P-MP and mesh architectures. FIG. 19 and FIG. 20 show examples of OFDM frame structure in the 802.16 standard.
In a P-MP architecture, as shown in FIG. 19, scheduling information (information indicating the slots for downlinks and the slots for uplinks allocated to each SS) is stored in the MAP messages (DL-MAP (FIG. 17), UL-MAP) included in broadcast message fields within the first DL (downlink) burst following the long preamble and FCH (Frame Control Header) for reception synchronization processing necessary for demodulation of wireless signals. By receiving a MAP message, an SS can determine the timing with which data for its own use arrives and the timing with which it can transmit. Below, a MAP message included in a broadcast message field in the first DL burst following an FCH is simply called a MAP message. The 802.16 standard is described in “Draft IEEE Standard for Local and Metropolitan Area Networks—Part 16: Air Interface for Fixed Broadband Wireless Access Systems”, IEEE P802.16-REVd/D5-2004, May 13, 2004.
In general wireless communication, due to such effects as shadowing arising from blockage by buildings and other obstructions between transmission/reception antennas, there exist dead zones in which communication with the BS is not possible, despite being within the service area. High frequencies must be used for high-speed wireless data communications, however, because wavelengths are shorter and the rectilinearity of radio waves is increased, further expansion of dead zones is anticipated. This is a serious problem for areal expansion of service.
This invention was devised in light of the above problems, and has as an object the provision of a wireless communication system, relay station device, and base station device enabling reduction of dead zones in which communication with the base station device is not possible and expansion of the service area.
By means of this invention, there are the advantageous results that dead zones in which communication with the base station device is not possible are reduced, and that the service area can be expanded.